[CG vertex shader] Surface normal to screen angle

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I've been struggling to get this working. I simply wish to take a surface normal and convert it to a screen angle to be used in a post processing effect.

As an example, assuming we're working with the highlighted surface on the sphere below, where the arrow is the normal, the 2D angle would obviously be PI/4 radians.

Sphere

Thanks for any and all help.

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Answer by Nabbz0rz · Jul 02, 2013 at 05:29 AM

Finally found the solution:

 float4 p = ComputeScreenPos(float4(v.normal, 1.0));
 
 o.theta = (atan2(p.y, p.x) / 6.28318530717958) + 0.5;

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[CG vertex shader] Surface normal to screen angle

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